The instant invention relates generally to super-conductivity and more particularly to a superconducting switch activated to "on" or "off" by an appropriate laser beam.
In the technology of electronics and energy conversion, superconducting devices and systems are becoming more and more prominent. The use of superconducting wave guides, superconducting magnetometers, superconducting magnets, superconducting inductors, superconducting electrical machinery, and other superconducting devices are now part of the state of the art. With many of these devices, the use of switches that are of the superconducting type are desirable, and sometimes required as part of the circuits involved.
Prior art superconducting switches generally consist of a length of superconductor with a method of heating it. For example, a small heating element may be wrapped around a small fraction of the length of the superconductor, or radiant light energy may impinge upon the superconductor to form a hot spot to raise its temperature. In either case, transition from the superconducting zero resistance to the resistive state is induced by means radiant energy heating the superconductor to above the transition temperature, and thus the superconductor becomes "normally conductive." Since most superconductors are generally highly resistive in their "normal" state, a bistable switch action is thus effected.
There are major disadvantages in the prior art switches. In the directly heated switch, a heater wire element must be wrapped around the superconductor and its leads brought out from the Dewar to an outside power source. Due to the heating, helium boil-off occurs along the length of the superconductor and heater wire element, especially where the heater wire is in contact with the helium bath and the superconductor. The radiant light energy type switch has some advantages over the wrapped heating wire element type, since the light can perform remote switching and the heating wire element is eliminated. However, the problems of helium boil-off and recooling are not eliminated because a great deal of light energy is required to heat the superconductor.
As suggested hereinbefore, it is well known that certain materials lose all apparent electrical resistance (superconduct) when subjected to very low temperatures near absolute zero. The transition from the resistive state to the superconductive state occurs abruptly at a critical temperature known as the transition temperature. It is also known that a transition from a superconductive state to a resistive state can be induced by applying a magnetic field to the superconductor. The magnetic field may be focused on the superconductor externally or induced internally by the flow of current in the superconductor wire when the current exceeds a critical value.
This invention capitalizes on the fact that superconductivity evidently arises from the pairing of electrons with equal and opposite momenta, and equal and opposite spins. Conversely, if superconducting is caused by pairing, then normalization is caused by depairing. Consequently, if the energy level of the electrons in the superconducting state is raised, as by pumping the electrons with a laser beam, so that the electrons are depaired, the superconducting material is normalized at the point of illumination.